Mycoplasma and Legionella

1. Mycoplasma and Legionella Ziad Elnasser, MD, Ph.D

2. Mycoplasma and Ureaplasma • No cell wall. • The smallest of free living organisms. • Associated with human disease: • Mycoplasma pneumoniae. • Mycoplasma hominis. • Ureaplasma urealyticum.

6. Microbiology • 0.2 – 0.3 μ pleomorphic, filamentous. • No cell wall, triple membrane contains sterols from tissue. • No stains, small genome. • Aerobic to facultative anaerobe, grows on Mycoplasma agar, inverted fried egg. • Binds to RBC’s on agar (Hemadsorption).

7. Mycoplasma pneumoniae • Pneumonia in young, any season. • Atypical pneumonia, scattered patches. • 10% of all Pneumonias. • Droplets, low infectious dose, temperate climates, 5-15y of age. • Sporadic endemic illness in families. • IP 2-15 days, infectivity 60%.

9. Pathogenesis • Trachea, bronchi, bronchioles and alveoli. • Cytadhesin (P1) binds to oligosaccharides containing sialic acid. • I Ag on surface of RBC’s. • Destroys cillia and causes desquamation. • Shedding 2-8 days before symptoms to 14 weeks after infection.

10. Immunity • Local and systemic. • CF antibodies, IgA antibodies 2-4 weeks. • Cold agglutinins IgM binds to I Ag on surface of RBC’s in 66% of cases. • Reinfection could occur. • Symptoms related to immune response, more severe in adults. • Raynaud’s phenomena.

11. Clinical Aspect • Mild tracheobronchitis, fever, cough, headache and malaise. • Less severe pneumonia (walking pneumonia). • X-ray shows patchy pneumonia, lower lobe. • Pleural effusion in 25% • Pharyngitis with fever, sore throat. • Otitis media, myringitis, and pneumonia.

13. Diagnosis • Clinically overlaps with viral and bacterial. • PMN’s in gram stain, bacteria not seen. • Isolation in special media, incubation for one week or longer. • Serology 4 fold increase in titre. • Cold agglutinins not specific, adenovirus, Epstien barr virus. • Immune assays, DNA hybridization, PCR.

16. Treatment • Erythromycin, Tetracycline. • Clarthromycin, Azithromycin. • Flouroquinilone.

17. Legionella • Gram negative bacilli, American legion convention. • Environmental pathogen. • Thin 0.5-0.7μm, filamentous 20μ long. Poor staining with gram but silver impregnation is used (Dieterle). • 3 flagella, motile, non spore former. • Outer membrane LPS but less compared to other g- bacteria.

21. Growth and Classification • L-cysteine, ferric ions, acidic pH. • 2-5 days needed for growth,ground glass colonies. • Catalase, oxidase, β lactamase. • 14 serogroups, L.bozemanii, L.dumoffii, L.micdadei. • Non infects humans.

22. Legionellosis • Inhalation, destructive pneumonia. • 1976 American Legion convention. • Other stored sera proved of previous pneumonia caused by Legionella. • Water reservoirs of large buildings. • No person to person transmission. • Not present in healthy people. • Low virulence to humans.

26. pathogenesis • Necrotizing multifocal pneumonia. • Alveoli and terminal bronchioles. • Inflamatory exudate contains fibrin, PMNs, macrophages, and erythrocytes. • Facultative intracellular pathogen→alveoli →alveolar macrophages→OMP binds C3 facilitates phagocytosis→Macrophage invasion potentiator OMP→cell entry→coiling phagocytosis→apoptosis and pore forming toxin.

28. Immunity • Virulence because it is intracellular. • CMI is the key. • Inhibition of MHC antigens. • Humoral immunity is less important. • Antibodies only enhancing phagocytosis.

29. Clinical aspects • Toxic pneumonia, myalgia, headache, fever, dry cough. • Chills, delirium, pleuritic chest pain, vomiting diarrhea. • Patchy infiltrates in chest x-ray. • Hepatic dysfunction. • Mortality is about 15%. • Pontiac fever.

30. Diagnosis • DFA. • Culture of infected tissues. • Lung aspirates, bronchoalveolar lavage, lung biobsy. • Buffered Charcol Yeast Extract (BCYE). • PCR. • Ag detection.

31. Treatment • Erythromycin. • Most legionella produces beta lactamases. • Tetracycline, rifampin, newer quinolones. • Azithromycin, clarithromycin. • Prevention:Hyperchlorination of water. • Heating water to more than 70C. • Silver and cupper ionization systems • Mists of water.

32. Pseudomonas • Gram negative bacillus. • Colonizers and contaminants, apportunistic diseases. • Bacteremia, arthritis, abscesses, wounds, conjunctivitis, UTI.

33. Ps. aerugenosa • Aerobic motile, g- rod, pale staining. • Colourfull water soluble pigments. • The most resistant to antimicrobial agents. • Simple growth requirements. • 20 – 40 C, Oxidase +, fruity odor. • Pyocyanin, Flourescin. • Lps , pili, polar flagellum, alginate (mannoronic and glucoronic acid) CF pts.

34. Extracellular products • Exotoxin A ( lecithinase, hemolysis, collagenase). • ADP-ribosylation of EF-2. • Exoenzyme S ADP-ribosylates vimentin acts as adhesin. • Elastases.

35. Diseases • Environment, throat, stool, > in hospitals. • Leukemia, Cystic fibrosis, and burns. • Humidifiers, inhalators, contact lenses sloutions, medications, disinfectans, sinks. • Food and water no problem. • CF chloride ion transport defect, thick mucus.

36. pathogenesis • Attachment favored by loss of fibronectin. • Exotoxin A, exotoxin S, and elastin. • Hemorragic destruction of blood vessles. • CS pts cells are less sialated increases receptors for the organism. • Biofilm (glycocalyx), alginate over produced. • Interfers with antibiotics and Immune mechanisms. • CMI deficient patients.

37. Clinical aspects • Apportunists. • pnemonia and in CF is chronic. • Otitis externa, swimmers ear, in DM. • Ecthyma gangrenosum. • Diagnosis is simple.

38. Treatment • Most resistant to penicillin, ampicillin, cephalothin, tetracyclin, streptomycin, chloramphenicol, sulfonamide. • New aminoglycosides. • Third and fourth generation cephalosporins. • Carbapenems and flouroquinolones. • CF aerosolized tobramycin. • Vaccines tried in CF some improvement. • Burkholderia, Acinetobacter, aeromonas and pleisomonas.